Cytoplasmic genetic effects and growth of hybrid mice.

Variation in cellular biochemical functions controlled by cytoplasmic genes was studied in relation to phenotypic differences between progeny of reciprocal hybrid female mice. Least squares procedures were used to test for differences in mitochondrial respiratory metabolism and in capacity for ATP synthesis, and differences in growth of progeny of hybrid dams. Under identical nuclear influences, mitochondria of A/J and C57BL/6J cytoplasms differed (P less than .10 to P less than .01) from those of BALB/cJ cytoplasm in energy conservation. No differences were detected in mitochondrial efficiency between BALB/cJ cytoplasm evaluated in different nuclear environments. Three-way cross progeny of C57BL/6J x BALB/cJ reciprocal hybrid females mated to DBA/2J males differed (P less than .05) in litter weight at weaning and 1 wk and 2 wk postweaning. The F2 progeny of reciprocal C57BL/6J x BALB/cJ dams and F2 and three-way cross progeny of reciprocal A/J x BALB/cJ dams did not differ in weight at any age measured. Across all genotypes of dam, rank correlations of mitochondrial traits with F2 litter weights were nonsignificant. Observed variation in mitochondrial functions partially controlled by cytoplasmic genes did not limit mouse growth under these experimental conditions.